It costs the T about $12 for every mile a subway train travels, the fifth costliest among the nation’s 15 similar rail systems. But because those expenses are spread among so many passengers at the T, it costs $1.82 to carry each passenger, the third least expensive system in that regard, according to the most recently available national data from 2007 budgets.
Unlike systems that use a single type of car for all their lines, the T’s subway cars vary in length and design and do not run interchangeably. That increases costs.
In Chicago, the El runs a standard vehicle on eight of its lines. In Boston, “you need separate garages, separate storerooms, separate maintenance facilities,’’ said Frederick Salvucci, a former transportation secretary who teaches at MIT.
The T also uses separate operating rules for each line. The Blue Line, for example, runs with only one operator on each train, while the other two lines require two operators, unlike almost every other transit system in the nation.
It is considered the busiest of the 27 American light-rail systems operating, many of which are relatively new and located in cities such as Charlotte, N.C., and Minneapolis.
The Green line is full of quirks. Downtown, it runs underground like a subway. In some locations, it runs above ground on its own tracks. And in other areas, it runs in and out of highway traffic like a bus. To complicate matters further, the MBTA also classifies the Mattapan Trolley, a vintage 2.6-mile loop track through Dorchester, Milton, and Mattapan, as light rail. It runs updated 1940s-era cars.
Those differences can make the system more costly to run than some more modern light-rail systems, which were built to run above ground and apart from car traffic, with more automation and fewer employees.
The Green Line costs about $21 for every mile it travels, the ninth most expensive system in that regard. But it is fourth least expensive per passenger, at $1.72.
The system’s 1,000-bus fleet has at least five types of equipment, including buses of two different sizes that run on diesel, some that run on compressed natural gas, others that run on electric wire, and dual-mode buses that alternate between overhead electrical wire and diesel fuel. The T will introduce a sixth type of bus, a hybrid diesel, sometime next year.
But commuters have complained at times about late service on the trains, which ranked among the tardiest in the country in a Globe survey conducted in December 2007.
The operating company, Massachusetts Bay Commuter Railroad Co., has improved on-time performance significantly in recent months, with more than 90 percent of trains arriving within five minutes of their scheduled time every month this year. Managers hope that the T agrees to extend its current contract by two years, through 2013.